Conditions for landslides in fine-grained soils
Description
The product provides comprehensive information on the conditions for landslides in fine soil. The information is intended to be used in the early planning phase to identify areas where landslide hazards may occur and where further assessments/investigations may need to be made.
The information is intended for use only in areas with fine-grained soils (mainly clay and silt). Thus, it does not provide information on conditions for landslides in moraine areas (which, depending on the grain size composition, may have properties that are potentially landslide sensitive). This applies in particular to areas in mountainous environments where slopes are steep and the grain size of the moraine is sometimes fine-grained. This product can therefore give a misleading picture in these mainly mountainous areas.
The information is based on a calculation algorithm (Tryggvason et al., 2014) that, based on soil type (according to SGU's product Soils 1:25 000 - 1:100 000), terrain model (Lantmäteriet's national elevation model) and critical slope (1:10 = 5.7 degrees = 10%), defines areas of fine-grained soil that have conditions for landslides.
These areas have then been further processed in the GIS environment to minimize systematic errors. The final result in this product is called areas of care.
The slope propensity of a clay layer depends not only on the slope of the ground, but also on its technical characteristics. The method does not take this into account but considers all soil layers of certain soil type (mainly silt and clay) as landslide sensitive at certain slopes. This means that in many of the identified areas of care, the characteristics of the clays are such that there is hardly any risk of landslides, despite the fact that the slope criterion is met.
As a complement to the modelling based on slope analysis, the product also includes a simpler GIS analysis based mainly on proximity to water.
Basic geotechnical/geological competence is necessary to be able to interpret the information correctly.
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